Topic - Best videocard for offloading video playback?

Hi. I'm trying to build a htpc-like system for video playback under Linux. Its a (relativitly) old HP EVO D530 system with a SFF agp slot. Since the 2x pci slots will be used for other purposes, i was wondering what video card i can count on to offload most of the mpeg2/mpeg4 (includeing Xvid and others)
decodeing. So far my choices seem to be the Nvidea 6200 or the ati radeon 9250. If i need to use X for hardware accel to work, i dont really care. Thankx in advance for your help!